Process for the recovery and purification of naphthenic acids



Jan. 9, 1951 J. G. DUNLAP PROCESS FOR THE RECOVERY AND PURIFICATION 0F'NAPHTHENIC ACIDS Filed Sept. 24. 1948 P. O 1U n. e V n s mr L n u 3 G. nTm J l:O Ow( if .rZmI/JO@ Uw ef a r O u Lv G 7 Aw. UQ .D

Patented Jan. 9, 1951 PROCESS FR THE RECOVERY AND PURIFI- CATON OFNAPHTHENIC ACIDS John G. Dunlap, Staten Island, N. Y., assignor toStandard Oil Development Company, a corporation of Delaware ApplicationSeptember 24, 1948, Serial No. 51,024

Claims. (Cl. 2260-514) The present invention relates to a process forthe separation and purification of naphthenic acids found in petroleumoils. The invention is more particularly concerned With the productionof high yields of high quality low molecular weight naphthenic acidswhich are suitable for use in paints as driers. YIn accordance with thepresent invention petroleum oils containing relatively high andrelatively low molecular weight naphthenic acids are treated with acaustic solution in order to remove these acids. The caustic solution isthen treated in an initial stage with a suitable reagent in order topartially regenerate a portion of the naphthenates. The relatively highmolecular weight naphthenic acids regenerated in the initial stage areremoved along with unsaponicable oily constituents. The relatively lowmolecular weight naphthenates are then completely regenerated in asecond stage to produce high yields of low molecular Weight naphthenicacids suitable as paint driers and the like. Y

It is well known in the art to segregate naph` thenic acids frompetroleum oils containing the same. For example, one method is to treata petroleum oil fraction with a caustic or equiva. lent reagent to formthe corresponding naphthenates. The naphthenic acids are thenregenerated by treating the naphthenates with sulfuric acid. Theresulting crude naphthenic acids containing unsaponiable oilyconstituents arethen subjected to a distillation operation wherein theoily constituents are segregated from the desired fractions ofnaphthenic acids.v

This method is not entirely satisfactory for the production of highquality naphthenic acids par'- ticularly when it is desired that theseacids have an acid number above about 240 and be relatively free ofunsaponiiiable oily constituents. In accordance with the presentinvention, high Iquality naphthenic acids in good yields are obtained.The invention may be readily underrstood by referring to the drawingillustrating an means of line 32. The treated oil is withdrawn from zone3B by means of line 33 and further refined as desired. Usually thisstream is passed to a cracking operation. The spent caustic phase iswithdrawn from zone 30 by means of line 2 and introduced into an initialregeneration stage l. tion is contacted under controlled conditions withan acidwhich for the purpose of illustration is assumed to be a 98%sulfuric acid. The .acid is introduced into initial stage l by means ofline 3. Suiiicient acid is introduced to convert approximately 10% ofthe naphthenates to their corresponding naphthenic acids.

The partially treated naphthenic acids and naphthenates along withunsaponiable oily constituents are removed from z one l by means of line4 and introduced into settling zone 6. Prior to introducing the streaminto Zone B, a solvent for the naphthenic acids is introduced into line4 by means of line 5. For the purpose of .illustration it is assumedthat the solvent comprises ether containing from about 3-6 carbon atomsin the molecule. In zone 5 an ether phase containing naphthenic acidsand unsaponiiable oily constituents forms as Well as a naphthenatephase. The solvent extract `phase is Withdrawn from zone E by means ofline l and may be handled in any manner desirable to segregate the highmolecular weight naphthenic'acids and the oily constituents.

" The naphthenate phase containing relatively.

low molecular weight constituents is withdrawn from zone 6 by means ofline 8 and introduced into a secondary regeneration stage 9. Sulfuric oran equivalent acid is introduced into stage 9 by means of line l0 underconditions to completely convert the remaining naphthenates tocorresponding naphthenic acids. The solution is withdrawn from thebottom of stage 9 by means of line Il and introduced into settling zonel2 wherein the spent acid is segregated and Y removed by means of lineI3. The naphthenic acid phase of a relatively high purity andsubstantially completely free of oily constituents is removed from zonel 2 by means of line I4.

`As pointed out heretofore, the present invention is concerned with atwo-stage regeneration process for the recovery of naphthenic acids. Theinvention is particularly adapted for the In this stage, the spentcaustic solu` treatment of petroleum oils boiling in the general rangefrom about 400-900 Also, as pointed out heretofore, it is desirable thatthese naphthenates if they are to be used as driers in paints must havean acid number of not less than about 240. Furthermore, if the processis to be successful the yield of the high quality naphthenic acids mustbe high.

The naphthenic acids present in petroleum oils have molecular weightsvarying appreciably, as for example, in the range from about 160 to 360and higher. The acid numbers of these na-phthenic acids likewise varyappreciably,` as for example, in the range from about 30 to 300.

These acid numbers are a function of the acid molecular weight and theunsaponiable oil content. acids have been a greater solubilizing" actionon the unsaponiiiable oils than the lower molecular weight acids.Naphthenic acids having a molecular Weight in the range from about 180to 275 have exhibited acid numbers in a descending range from about 312to 204. V".Iherefore, the higher the molecular weight and theunsaponiable oil content, the lower the acid number.

The reagent used to generate the naphthenates in the -respective stagesYpreferablyW comprises silfuric acid or carbon dioxide. If sulfuricacidis employed it is preferred "that the concentration' o fthe acid bei'n'th'e range from about 9 5 to 100%. If carbon dioxide is` employed,it may be employed assuch 6r theV caustic extract may be treated withgascontainiiig carbon dioxide.` Inv general, atmospherictemperatures andpressures ara'e'mploye'd in theacidication'stages Y"The presentinvention may be readily understoo'dlbf'th'e following examplesillustrating the s EXAMPLE I A petroleum oil boiling in the range fromabout 400%750" F. and secured from a Venezuelan crude was contacted witha6 B. sodium hydroxide solution.' The spent caustic was segregated'intovarious portions and acidiiied in two stfag'es with 95% to 98% sulfuricacid'. In an initial run, one portion was completely acidied ina singlestage. In 4 subsequent runs a two-v stage operation was employed whereinthe extent towhich the naphtlienates were acidiiied in the initialstages was varied from 5% to 30%. The results of these runs aretabulated below.

Table l SINGLE STAGE ACiDIFiCArION RUN #l i A ,cid NQ.l ...I 219 Aver.mol. weight Vof acids 2,25 M015 acid L 87:9 M015 Oil 12.1 Percent oil inacid 12.1

'Two-STAGE AoiDirIoATioN First Stage, Second Stage, NaphthenicNaphthenic Acid Regen- Acid Regeneration eration RUN #2 5% lumaiLiberation;

-,Acid No.- 31 231 Aver. Mol. Weight of Acids 272 223 Mols Acid 4.4 83.5'Mills Oil S. 7'v 8.4 MolPer Ce,r O 45. 7 9.15

Yield: l

VMol Per Cent Acid 5 195 Weight BerQent Aeid, 10 90 The highmolecular'weight naphthenic Table I-Continued TWO-STAGEACIDIFICATIoN-Continued First Stage, Second State, Naphthenic NaphthenicAcid Regen- Acid Regeneration eration RUN #3 10% Liberation:

Acid No 240 Aver Mol Weight of Acids 270 222 Mols c 8.8 79.1 Mols Oil6.7 5.4 Mol Per Cent Oil in Acid..- 43.3 6.4 Yield:

Mol Per Cent Acid 10 90 Weight Per Cent Acid 18 82 RUN #4 20%Liberation:

Acid No 107 247 Aver. Mol. Weight ol' Acids 262 220 Y 17.6 70.3 8.8 3.333. 2 4. 5

Mol Per Cent Acid 20 80 Weight Per Cent Acid 29.4 70. 6

RUN #5 30% Liberation:

. Acid No 142 255 Aver. Mol. Weight of Acids 259 214 Mols Acid 26.461..5 Mols Oil 9. 1 3.0 Mol Per Gent Oil in Acid 25. 4. 7 Yicld:

Mol Per Cent Acid 30 70 Weight Per Cent Acid. 40.1 59.0

It is to be observed that in runs #2 to #5 the unsaponiable oils arepresent in a very high con-v centration with the naphthenic acidssegregated inthe initial stage. It is also to be observed that in' runs#Sto #5 the acid number of the product secured in the second stage is240 or better.V HoW-z ever, with respect to runs #4 and #5 the yieldsdropped off appreciably (weight per cent) as compared to the resultssecuredin run #3. It is therefore apparent that ifa naphthenic acid isto be' produced which has an acid number in exfcess of 240, it will benecessary to liberate lfrom 10A to 30 mol. per cent of the naphthenicacids in' an initiall stage and thus removeunsaponiable oilyconstituents therewith. Itis alsoapparent that if good yields are to beobtained `Awhen treating a gas oil boiling in the range from about400-750` F., the extent of the acidication in the initial stage shouldbe in the range from about 10 to 20%.

A petroleum oil boiling in the range from about (500E-900 F. and securedtrom a Venezuelan crude was contacted With a 6 B. sodium hydroxidesolution. The spent caustic was segregated into various portions andacidiiied in twoA stages. In an initial run one portion was completelyacidiiied in a single stage. In 4 subsequentfruns a two-stage operationwas employed wherein the extent to which the naphthenates were acidiiedin the initial stages was varied from 4 0 to '10%. The results of theseruns are tabulated below,

Table II-Contz'nued Two-STAGE AoIDIFIoATIoN First Stage, Second Stage,Nanhthenic Naphthenic Acid Regen- Acid Regeneration eration RUN #2 PerCent Liberation: 40 Acid No 96.8 228 325 235 31. 6 48 l 13.9 6. 5 MolPer Cent Oil in Acid 30. 6 11.9 Yield:

Mol Per Cent Acld 40 60 Weight Per Cent Acid 56. 4 43. 6

RUN #3 Per Cent Liberation:

5o- Acid N0 112 238 Aver. Mnl. Weight of Acids 315 227 Mols Acid-- 39. 839. 8 Mols Oil 14.7 5. 7 Mol Per Cent 26.9 12. 5 Yield:

Mol Per Cent Acid 50 50 Weight Per Cent Acid 65. 2 34.8

RUN #4 r Cent Liberation:

60 P.(cid No 124 250 Aver., Mnl. Weight of Acids 307 217 Mols Acid 47. 831. 8 Mols Oil 15.3 4. 9 Mol Per Cent Oil in Acid 24. 2 13. 4 Yield:

Mol Per Cent Acid 60 40 Weight Per Cent Acid 73. 6 26. 4

RUN #5 140 263 289 208 55. 7 23. 9 l5. 6 4. 8 Mol Per 21. 9 16. 7 Yield:

Mol Per Cent Acid 70 30 Weight Per Cent Acid 81.1 18.9

The data illustrated in Table II, runs #2 to #5, show a very highconcentration of unsaponifable oils segregated with naphthenc acids inthe initial stage. The acid number of the product see cured in thesecond stage with respect to runs #3 to #5 is about 238 or better.However, with respect to runs #4 and #5 the yields drop off appreciably(weight per cent) as compared to the results secured in run #3. It istherefore apparent that if a naphthenic acid is to be produced which hasan acid number in excess of 238, it will be necessary to liberate from50 to 70 mol. per cent of the naphthenic acids in an initial stage andthus remove unsaponiiable oily constituents therewith. It is alsoapparent that ify good yields are to be obtained when treating a gas oilboiling in the range from about 600-900 F., the extent of theacidification in the initial stage should be in the range from about 50to 60%.

EXANEPLE III The naphthenic acids produced in run #1 of Example I weresubjected lto distillation and 3 fractions segregated, the results areas follows:

10 Yld 6 Table III-Continued DISTILLATION OF SINGLE STAGE ACIDIFI'CATIONPRODUCT FRACTION S 1 Acid No Aver. Mol. Weight of Acids Mols Acid MolPer cent Acid Weight Per cent Acid.--

It is to be observed that fraction #2 exhibits an appreciable drop inyield F(weight per cent acid) when compared to the product yield securedin the second stage of run #2, Table I, Example I. In order to obtainnaphthenic acids having an acid number of 240 or better in adistillation process, it requires closer fractionating of the acidiednaphthenates. The yield (weight per cent acid) would be considerablyylower than that shown for fraction #2.

EXAMPLE IV `The extent to which unsaponiable oil will affect the acidnumber is readily apparent from the following test data. A naphthenicacid fraction boiling in the range from 400-750 F. has naphthenic acidsthe molecular weights of which vary from 180 to 275. The respective acidnumbers vary from about 312 to 204. If this fraction should containabout 10% of unsaponifable oily constituents, tbe acid number would beabout 184.

What is claimed is:Y

1. Process for the segregation of llow molecular weight naphthenic acidsof high quality from petroleum oils containing the same, which compriseswashing a feed petroleum oil containing relatively high and relativelylow molecular weight naphthenic acids with a caustic solution,separating the respective oil and caustic phases, treating saidseparated caustic phase in an initial regeneration stage with a reagentadapted to coni vert at least 10% of the relatively high molecularweight naphthenates into their correspondingly high molecular weightnaphthenic acids, extracting the relatively high molecular Weightnachthenic acids with a suitable solvent. whereby the relatively highmolecular weight naphthenic acids` and unsaponiable oil constituents aredissolved in said solvent, separating the solvent extract phase from therelatively low molecular weight naphthenate phase, and thereafter in asecond stage completely regenerating the relatively low molecular weightnaphthenates with a suitable reagent whereby high quality low molecularweight naphtllenic acids substantially completely free of unsaponifiableoil constituents are secured.

2. Process as dened by claim 1 wherein said feed petroleum oil boils inthe range from about 400 F. to about 750 F. and wherein said causticphase is treated in said initial regeneration stage under conditions toregenerate from 1.6 to 30% which comprises washing said petroleum oilwith a,l caustic solution, separatingV the caustic phase from thetreated cil, treating said caustic phase in an initial regenerationstage with a reagent adapted to convert at least 10% of the naphthenatesinto corresponding naphthenic acida,

treating the solution with a solvent to remove the naphthenic acids andentrain unsaponiable constituents, removing the solvent extract andtreating the remaining naphthenates in a sec.- ondary stage underconditions to convert the same to corresponding naphthenic acids,whereby high yields of high quality naphthenic acids are secured.

5. Process for the production of high yields of 10W moiecular weightnaphthentic acids having anacid number of at least 240 from a petroleumoil boiling in the range from about 600 F. to 900 F. which compriseswashing said petroleum oil with a caustic solution, separating thecaustic phase from the treated cil, treating said caustic phase inl aninitial'regeneration stage with a reagent adapted to convert about 50%of the naphthenates into corresponding naphthenic acids, treating thesolution with a solvent to remove the naphthenic acids and entrainunsapon- 8 i iable constituents,- removing the solvent extract andtreating the remaining naphthenates in a secondary stage underconditions to convert the same to corresponding naphthenic acids,whereby high yields of high quality naphthenic acids are secured.

JOHN G. DUNLAP.

REFERENCES CITED The following references are of record in the iile ofthis patent:

UNITED STATES PATENTS Number Name Date 1,886,647 Coleman Nov. 8, 19321,984,432 Robinson Dec. 18, 1934 1,993,259 Buc Mar. 5, 1935. 2,000,244Merrill et al May 7, 1935 2,039,106 l Nelson et al Apl. 28, 19362,093,001 B10-unt Sept. 14, 1937 2,131,938 Donker Oct. 4, 1938 2,170,506Reiber Aug. 22 1939 2,296,039 Knowles et al Sept. 15, 1942 2,324,467Brandt et al July 20, 1943

1. PROCESS FOR THE SEGREGATION OF LOW MOLECULAR WEIGHTT NAPHTHENIC ACIDSOF HIGH QUALITY FROM PETROLEUM OILS CONTAINING THE SAME, WHICH COMPRISESWASHING A FEED PETROLEUM OIL CONTAINING RELATIVELY HIGH AND RELATIVELYLOW MOLECULAR WEIGHT NAPHTHENIC ACIDS WITH A CAUSTIC SOLUTION,SEPARATING THE RESPECTIVE OIL AND CAUSTIC PHASES, TREATING SAIDSEPARATED CAUSTIC PHASE IN AN INITIAL REGENERATION STAGE WITH A REAGENTADAPTED TO CONVERT AT LEAST 10% OF THE RELATIVELY HIGH MOLECULAR WEIGHTNAPHTHENATES INTO THEIR CORRESPONDINGLY HIGH MOLECULAR WEIGHT NAPHTHENICACIDS, EXTRACTING THE RELATIVELY HIGH MOLECULAR WEIGHT NAPHTHENIC ACIDSWITH A SUITABLE SOLVENT, WHEREBY THE RELATIVELY HIGH MOLECULAR WEIGHTNAPHTHENIC ACIDS AND UNSAPONIFIABLE OIL CONSTITUENTS ARE DISSOLVED INSAID SOLVENT, SEPARATING THE SOLVENT EXTRACT PHASE FROM THE RELATIVELYLOW MOLECULAR WEIGHT NAPHTHENATE PHASE, AND THEREAFTER IN A SECOND STAGECOMPLETELY REGENERATING THE RELATIVELY LOW MOLECULAR WEIGHT NAPHTHENATESWITH A SUITABLE REAGENT WHEREBY HIGH QUALITY LOW MOLECULAR WEIGHTNAPHTHENIC ACIDS SUBSTANTIALLY COMPLETELY FREE OF UNSAPONIFIABLE OILCONSTITUENTS ARE SECURED.